In an electrophotographic printer of this type, it is desirable that the photoconductor and transfer drums for maintenance and inspection should easily be detachable. And, as the prior art which allows such easy detachment there is known a drum apparatus disclosed in JP Patent No. 3037279, though it is a little different in the field of art concerned.
The drum apparatus of this prior art relates to a rotary press equipped with at least one drum whose journals are borne by a pair of side walls. One of these side walls has a door or removable cover swingably supported on the side wall, and the drum is supported by the door or cover via a bearing so that swinging the door or cover open opens an end face side of the drum.
And, the end face side of the drum facing the door is provided with a separable area which comprises conically shaped portions in a pair having a truncated conical projection and a truncated conical recess fitted with the projection. In the separable area, a journal or a portion of the journal can be separated from the body of the drum and can be swung by the door together with the bearing.
In this prior art, the bearing and the drum may be coupled together by the recessed and projecting conical portions and their axial centers may be positioned by the conical portions.
In the prior art mentioned above, the conical portions are hard to machine with precision and the center positions of their recessed and projecting shapes are easily misaligned. The conical recess and projection when connected together tend to produce a partial contact, and there arises, e. g., the problem that the wear of a portion of the partial contact goes on quickly. Besides, depending on an angular makeup of the conical shapes a thrust load develops as a component of force of a radial load with respect to an axis. As a result, the problem arises that a run-out may be created of the axial center unless all the components in a direction of thrust are fixed in the thrust direction.
It is an object of the present invention to provide an electrophotographic printer in which a photoconductor and a transfer drum can be supported in a simple component construction and in the makeup free from misalignment and development of thrust load.